Testis Development
Introduction
The male gonad is the testis. The initial difference in male and female gonad development are dependent on testis-determining factor (TDF) the protein product of the Y chromosome SRY gene. Recent studies have indicated that additional factors may also be required for full differentiation.
The seminiferous tubules are considered the parenchyma of the testis.
Links: Y Chromosome | Week 1 - Spermatogenesis | Ovary | Puberty | original page
Development Overview
Sex Determination
- Humans (week 5-6)
- Germ cells migrate into gonadal ridge
- Gonads (male/female) identical at this stage, Indifferent
Gonad Development
- dependent on sex chromosome
- Y testes
- No Y ovary
SRY
SRY protein (Testes determining factor, TDF) binds DNA Transcription factor, Bends DNA 70-80 degrees
Internal Genital Organs
- All embryos form paired
- Mesonephric duct, see kidney development
- Paramesonephric duct, Humans 7th week Invagination of coelomic epithelium Cord grows and terminates on urogenital sinus
- Male Gonad (testes) secretes Mullerian duct inhibitory factor (MDIF) which causes regression of paramesonephric duct
- Male Gonad (testes) secretes Testosterone which retains mesonephric duct
External Genital Organs
- All embryos initially same (indifferent)
- Testosterone differentiates male
Additional Images
molecular model of SRY and DNA interaction
Historic image of early testis development
Historic image of later testis development
labelled start image of animation of testis descent
labelled end image of animation of testis descent
adult testis histology overview
adult testis histology overview
adult testis histology Seminiferous tubules and Tunica albuginea
adult testis histology Seminiferous tubule and Interstitial cells
